GROTON, Conn. (AP) — About 2,500 workers at Electric Boat shipyard in Connecticut plan to strike on May 18 if a tentative contract agreement is not reached with the submarine builder, the union president announced during a rally Thursday.

About 300 union members cheered the announcement made by Bill Louis, president of the Marine Draftsmen’s Association-United Auto Workers of America, Local 571, The Day of New London newspaper reported.

“We’re officially putting the company on notice that if we don’t have an agreement at 11:59 p.m., we strike at midnight May 18,” Louis told the union members, most of whom are essentially responsible for designing the U.S. Navy's nuclear submarine fleet.

A message was left seeking comment with an EB spokesperson in Groton.

The looming strike comes as a day after the U.S. Navy awarded EB's parent company, General Dynamics, a contract worth more than $12.4 billion for the construction of two Virginia class submarines authorized during last fiscal year. The funding also covers improved worker pay.

More than two-thirds of the union membership voted last month to authorize a strike if a deal couldn't be reached on a new contract.

The union’s contract expired on April 4, but leadership has agreed to continue bargaining with EB. They’ve demanded higher wages over four years, the restoration of pension benefits for all members, cost of living adjustments and profit sharing with General Dynamics, EB’s parent company, among other changes.

“The clock has run out on corporate greed,” UAW President Shawn Fain told members during a rally last month. “And I’ll tell you, this is a new UAW where the membership comes first and we refuse to aim low and settle lower.”

EB's earlier now-expired offer had included a 23.3% general wage increase over the life of the contract, plus benefits and an increased retirement package.

The company has acknowledged it has been “actively preparing a business continuity plan in the event of a work stoppage,” adding it will “not waver from our commitment to continue building submarines, the nation’s top national security priority.”